Effect of UV irradiation on rheological properties of tragacanth gum

In this study, the effect of ultraviolet irradiation (UV254) in various irradiation times on rheological properties, intrinsic viscosity and apparent viscosity, and clarity of tragacanth gum was studied. The plot of specific viscosity (ηsp) as a function of concentration to obtain critical overlap concentration or c* showed a shift from 0.11 to 0.09 g/dL after 80 min UV exposure. The extrapolation of reduced viscosity (ηred) and inherent viscosity (ηinh) to zero shear concentration was also investigated. The extent of intrinsic viscosity was reduced from 13.3 to 7.34 dL/g resulted from UV irradiation after 80 min. The steady–shear properties of 0.2 g/dL aqueous solution of tragacanth gum in shear rate range of 0.1-400 s-1 at 40℃, showed the shear thinning behavior. Results of rheological measurement indicated a notable reduction in the consistency index after UV irradiation, certainly with a steeper slope at high time irradiation. The influence of UV irradiation on the flow behavior index was not significant. The clarity of the tragacanth gum was measured by UV-Visible in 660 nm and found that the clarity was increased by irradiation time.

Keywords:

Tragacanth gum , Critical overlap , Intrinsic viscosity , Shear thinning behavior